1. Field of the Invention
The present invention relates to a finder optical system and a camera having the system, and more particularly, to a finder optical system having an eyesight-adjusting function of correcting the deviation of the optical characteristics of the image viewed through an eyepiece, depending on temperature.
2. Description of the Related Art
Japanese Patent Application Laid-Open Nos. 2-230226 and 3-81748 disclose techniques for correcting the deviation of the optical characteristics of the image viewed through an eyepiece, due to a change of subject distance in a real-image finder.
Japanese Patent Application Laid-Open No. 8-122854 discloses a technique for converting the deviation of the optical characteristics of the image viewed through an eyepiece, due to changes in temperature, humidity, brightness, and the like.
In the conventional art disclosed in Japanese Patent Application Laid-Open Nos. 2-230226 and 3-81748, however, it is impossible to correct deviation of the optical characteristics of the image viewed through an eyepiece, due to changes in temperature, and it is therefore difficult to achieve high finder magnification. An optical system having high finder magnification requires glass lenses, which increases the manufacturing costs.
In contrast, in the conventional art disclosed in Japanese Patent Application Laid-Open No. 8-122854, deviation of the optical characteristics of the image viewed through an eyepiece due to changes in temperature is corrected by a part of an eyepiece. However, when the deviation of the optical characteristics of the image viewed through an eyepiece with respect to a subject image is corrected by the eyepiece system, the visual field frame and the images displayed inside and outside the visual field frame are not clearly viewed. In a zooming optical system, since the extent of the optical characteristics of the image viewed through an eyepiece to be corrected substantially changes, the stroke of a correction lens is too great, and the amount of correction must be changed very much according to the zooming position, which enlarges and complicates the structure.
Accordingly, an object of the present invention is to overcome the above-described problems in the conventional art, and to provide a finder optical system in which a visual field frame and the images displayed inside and outside the visual field frame are clearly viewed even when the deviation of the optical characteristics of the image viewed through an eyepiece is corrected based on temperature information.
To achieve the above-noted object, according to one aspect, the present invention relates to a finder optical system for observing an object therethrough, comprising a variable-power objective optical system, an eyepiece optical system for guiding light from the object via the objective optical system to an observer, and adjustment means for changing the optical characteristics of an image of the object observed by the observer through the eyepiece optical system based on information about the temperature of the finder optical system, the distance from the finder optical system to the object, and the zoom position of the objective optical system.
According to another aspect, the present invention relates to a finder optical system for observing an object, comprising an objective optical system, an eyepiece optical system for guiding light from the object via the objective optical system to an observer, and adjustment means for changing the imaging position of the objective optical system based on temperature information.
According to still another aspect, the present invention relates to a camera comprising a photographing optical system for forming an image of an object on a photosensitive plane, and a finder optical system for observing the object therethrough. The finder optical system comprises a variable-power objective optical system, an eyepiece optical system for guiding light from the object via the objective optical system to an observer; and adjustment means for changing the optical characteristics of an image of the object observed by the observer through the eyepiece optical system based on information about the temperature of the finder optical system, the distance from the finder optical system to the object, and the zoom position of the objective optical system.
According to still another aspect, the present invention relates to a camera comprising a photographing optical system for forming an image of an object on a photosensitive plane, and a finder optical system for observing the object therethrough. The finder optical system comprises an objective optical system, an eyepiece optical system for guiding light from the object via the objective optical system to an observer, and adjustment means for changing the imaging position of the objective optical system based on temperature information.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.